Tecumseh 17hp trouble cranking past compression

[redveloce]

Hello,

This is my first technical post here, but I've been playing around with and tweaking small engines since I was a kid. This one has me baffled.

I have a mid-late 90's Yard Machines 662 hydrostatic lawn tractor with a Tecumseh 17hp OHV engine that was given to me with electrical and possible engine problems. There was a short that burned up some wiring, so I simplified the harness, bypassing the safeties and isolating the ignition and starter circuits for troubleshooting.

Currently the engine cranks with the electric start until it hits the compression stroke, then won't push through the compression. It turns freely and easily by hand until it gets to the compression, then it takes everything I can do to get it past the compression.

Things I have done:

- New Battery
- New Starter
- New Starter solenoid
- New Spark plug
- Cleaned wiring connections to battery, solenoid, ground, and starter
- Checked, adjusted, checked, and triple checked valve adjustment

I can get it to barely push past the compression stroke if I assist with my craftsman jump starter hooked directly to the starter, and it does try to fire on starting fluid at that point, but won't hit more than once or twice.

Any ideas on what might cause this? Maybe a stretched connecting rod?

Thanks ahead of time for any help and ideas!

 

[ILENGINE]

Either the valve clearances are out of spec, or the compression release has broken on the camshaft.

 

[Rivets]

ILengine hit it right on the head.

 

[ASEAudie]

Yep, ACR is most likely bad.

 

[redveloce]

Thanks for the replies. I didn't realize the engine had a compression release, but it makes sense. Just getting the search term "ACR" gave me the search 'keys to the kingdom' returning a treasure trove of information regarding people having the same problems with the same engine. Thanks again!
James